Revert of Mojo C++ bindings: always use MultiplexRouter with InterfacePtr/Binding.

mojo/public/cpp/bindings/interface_ptr.h

Index: mojo/public/cpp/bindings/interface_ptr.h
diff --git a/mojo/public/cpp/bindings/interface_ptr.h b/mojo/public/cpp/bindings/interface_ptr.h
index bd77ead04285c2173f1b69b574af76ccec8212eb..29d362e0f6122377f6998b9c2ad64907f3ea938c 100644
--- a/mojo/public/cpp/bindings/interface_ptr.h
+++ b/mojo/public/cpp/bindings/interface_ptr.h
@@ -201,7 +201,8 @@
   }
 
   // DO NOT USE. Exposed only for internal use and for testing.
-  internal::InterfacePtrState<Interface, true>* internal_state() {
+  internal::InterfacePtrState<Interface, Interface::PassesAssociatedKinds_>*
+  internal_state() {
     return &internal_state_;
   }
 
@@ -209,7 +210,9 @@
   // implicitly convertible to a real bool (which is dangerous).
  private:
   // TODO(dcheng): Use an explicit conversion operator.
-  typedef internal::InterfacePtrState<Interface, true> InterfacePtr::*Testable;
+  typedef internal::InterfacePtrState<Interface,
+                                      Interface::PassesAssociatedKinds_>
+      InterfacePtr::*Testable;
 
  public:
   operator Testable() const {
@@ -225,7 +228,8 @@
   template <typename T>
   bool operator!=(const InterfacePtr<T>& other) const = delete;
 
-  typedef internal::InterfacePtrState<Interface, true> State;
+  typedef internal::InterfacePtrState<Interface,
+                                      Interface::PassesAssociatedKinds_> State;
   mutable State internal_state_;
 
   DISALLOW_COPY_AND_ASSIGN(InterfacePtr);